arXiv subjects

Amruta Mishra

Publications and source records attributed to Amruta Mishra.

At least 73 records · Page 4Linked to original sources

arXiv2010

Charmonium mass in hot asymmetric nuclear matter

We calculate the in-medium masses of J/$ψ$ and of the excited states of charmonium ($ψ$(3686) and $ψ$(3770)) in isospin asymmetric nuclear matter at finite temperatures. These mass modifications arise due to the interaction of the charmonium states with the gluon condensates of QCD, simulated by a scalar dilaton field introduced to incorporate the broken scale invariance of QCD within an effective chiral model. The change in the mass of J/$ψ$ in the nuclear matter with density is seen to be rather small, as has been shown in the literature by using various approaches, whereas, the masses of the excited states of charmonium ($ψ$(3686) and $ψ$(3770)) are seen to have considerable drop at high densities. The dependence of the masses of the charmonium states on the isospin asymmetry has also been investigated in the hot nuclear matter and is seen to be appreciable at moderate temperatures and high densities. These medium modifications of the charmonium states should modify the experimental observables arising from the compressed baryonic matter produced in asymmetric heavy ion collision experiments in the future facility of FAIR, GSI.

nucl-th↗

arXiv2009

D mesons in asymmetric nuclear matter at finite temperatures

We study the in-medium properties of $D$ and $\bar{D}$ mesons in isospin-asymmetric nuclear matter at finite temperatures using an effective chiral SU(4) model. The interactions of $D$ and $\bar{D}$ mesons with nucleons, scalar isoscalar meson $σ$, and scalar iso-vector meson $δ$ are taken into consideration. It is found that as compared to the $\bar{D}$ mesons, the properties of the $D$ mesons are observed to be quite sensitive to the isospin-asymmetry at high densities. At finite densities, the masses of $D$ and $\bar{D}$ mesons observed at finite temperatures are seen to be higher in comparison to the zero temperature case. The present study of the in-medium properties of $D$ and $\bar{D}$ mesons will be of relevance for the experiments in the future facility of the FAIR, GSI, where the compressed baryonic matter at high densities and moderate temperatures is expected to be produced. The mass modifications of $D$ and $\bar{D}$ mesons in hot nuclear medium can lead to decay of the charmonium states ($Ψ^{'}, χ_{c}, J/Ψ$) to $D\bar{D}$ pairs in dense hadronic matter. The isospin-asymmetric effects on the properties of the open charm mesons for the doublets $D=(D^0,D^+)$ and $\bar D=(\bar D^0,D^-)$ should show in observables like their production and collective flow in asymmetric heavy-ion collisions. The small attractive potentials observed for the $\bar{D}$ mesons may also lead to formation of the $\bar{D}$ mesic nuclei.

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arXiv2009

Kaon properties in (proto)neutron stars

The modification on kaon and antikaon properties of in the interior of (proto-)neutron stars is investigated using a chiral SU(3) model. The parameters of the model are fitted to nuclear matter saturation properties, baryon octet vacuum masses, hyperon optical potentials and low energy a kaon-nucleon scattering lengths. We study the kaon/antikaon medium modification and explore the possibility of antikaon condensation in (proto-)neutron star matter at zero as well as finite temperature/entropy and neutrino content. The effect of hyperons on kaon and antikaon optical potentials is also investigated at different stages of the neutron star evolution.

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arXiv2009

D-mesons in asymmetric nuclear matter

We calculate the in-medium $D$ and $\bar D$-meson masses in isospin asymmetric nuclear matter in an effective chiral model. The $D$ and $\bar D$ - mass modifications arising from their interactions with the nucleons and the scalar mesons in the effective hadronic model are seen to be appreciable at high densities and have a strong isospin dependence. These mass modifications can open the channels of the decay of the charmonium states ($Ψ^\prime$, $χ_c$, $J/Ψ$) to $D \bar D$ pairs in the dense hadronic matter. The isospin asymmetry in the doublet $D=(D^0,D^+)$ is seen to be particularly appreciable at high densities and should show in observables like their production and flow in asymmetric heavy ion collisions in the compressed baryonic matter experiments in the future facility of FAIR, GSI. The results of the present work are compared to calculations of the $D(\bar D$) in-medium masses in the literature using the QCD sum rule approach, quark meson coupling model, coupled channel approach as well as from the studies of quarkonium dissociation using heavy quark potentials from lattice QCD at finite temperatures.

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arXiv2009

LOFF and breached pairing with cold atoms

We investigate here the Cooper pairing of fermionic atoms with mismatched fermi surfaces using a variational construct for the ground state. We determine the state for different values of the mismatch of chemical potential for weak as well as strong coupling regimes including the BCS BEC cross over region. We consider Cooper pairing with both zero and finite net momentum. Within the variational approximation for the ground state and comparing the thermodynamic potentials, we show that (i) the LOFF phase is stable in the weak coupling regime, (ii) the LOFF window is maximum on the BEC side near the Feshbach resonance and (iii) the existence of stable gapless states with a single fermi surface for negative average chemical potential on the BEC side of the Feshbach resonance.

cond-mat.supr-con↗

arXiv2009

BCS BEC crossover and phase structure of relativistic system: a variational approach

We investigate here the BCS BEC crossover in relativistic systems using a variational construct for the ground state and the minimization of the thermodynamic potential. This is first studied in a four fermion point interaction model and with a BCS type ansatz for the ground state with fermion pairs. It is shown that the antiparticle degrees of freedom play an important role in the BCS BEC crossover physics, even when the ratio of fermi momentum to the mass of the fermion is small. We also consider the phase structure for the case of fermion pairing with imbalanced populations. Within the ansatz, thermodynamically stable gapless modes for both fermions and anti fermions are seen for strong coupling in the BEC regime. We further investigate the effect of fluctuations of the condensate field by treating it as a dynamical field and generalize the BCS ansatz to include quanta of the condensate field also in a boson fermion model with quartic self interaction of the condensate field. It is seen that the critical temperature decreases with inclusion of fluctuations.

hep-ph↗

arXiv2008

Kaon and antikaon optical potentials in isospin asymmetric hyperonic matter

The medium modifications of the energies of kaons and antikaons in isospin asymmetric hyperonic matter are investigated using a chiral SU(3) model. The isospin dependent medium effects, are important for asymmetric heavy ion collision experiments, as well as relevant for the neutron star phenomenology as the bulk matter in the interior of the neutron star is highly isospin asymmetric. The effects of hyperons on the medium modifications of the kaons and antikaons in the strange hadronic matter are investigated in the present work and are seen to be appreciable for hadronic matter with large strangeness fractions. The study of the K-mesons in the asymmetric strange hadronic matter can be especially relevant for the compressed strange baryonic matter which can result from asymmetric heavy ion collision experiments in the future accelerator facility FAIR at GSI.

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arXiv2008

Pairing in spin polarized two-species fermionic mixtures with mass asymmetry

We discuss on the pairing mechanism of fermions with mismatch in their fermi momenta due to a mass asymmetry. Using a variational ansatz for the ground state we also discuss the BCS -BEC crossover of this system. It is shown that the breached pairing solution with a single fermi surface is stable in the BEC regime. We also include the temperatures effect on the fermion pairing within an approximation that is valid for temperatures much below the critical temperature.

cond-mat.supr-con↗

arXiv2006

Color superconductivity with determinant interaction in strange quark matter

We investigate the effect of six fermion determinant interaction on color superconductivity as well as on chiral symmetry breaking. Coupled mass gap equations and the superconducting gap equation are derived through the minimisation of the thermodynamic potential. The effect of nonzero quark -- antiquark condensates on the superconducting gap is derived. This becomes particularly relevant for the case of 2-flavor superconducting matter with unpaired strange quarks in the diquark channel. While the effect of six fermion interaction leads to an enhancement of u-d superconductivity, due to nonvanishing strange quark--antiquark condensates, such an enhancement will be absent at higher densities for u-s or d-s superconductivity due to early (almost) vanishing of light quark-- antiquark condensates.

hep-ph↗

arXiv2006

Isospin dependent kaon and antikaon optical potentials in dense hadronic matter

Isospin effects on the optical potentials of kaons and antikaons in dense hadronic matter are investigated using a chiral SU(3) model. These effects are important for asymmetric heavy ion collision experiments. In the present work the dispersion relations are derived for kaons and antikaons, compatible with the low energy scattering data, within our model approach. The relations result from the kaonic interactions with the nucleons, vector mesons and scalar mesons in the asymmetric nuclear matter. The isospin asymmetry effects arising from the interactions with the vector-isovector $ρ$- meson as well as the scalar isovector $δ$ mesons are considered. The density dependence of the isospin asymmetry is seen to be appreciable for the kaon and antikaon optical potentials. This can be particularly relevant for the future accelerator facility FAIR at GSI, where experiments using neutron rich beams are planned to be used in the study of compressed baryonic matter.

nucl-th↗

arXiv2005

The properties of the D-meson in dense matter

We study the D-meson spectral density in dense matter within the framework of a coupled-channel self-consistent calculation taking, as bare meson-baryon interaction, a separable potential. Our coupled-channel model generates dynamically the $Λ_c(2593)$ resonance. The medium modifications of the D-meson properties due to Pauli blocking and the dressing of D-mesons, nucleons and pions are also discussed. We found that the coupled-channel effects in the self-consistent process reduce the in-medium effects on the D-meson compared to previous works.

hep-ph↗

arXiv2004

Color superconducting 2SC+s quark matter and gapless modes at finite temperatures

We investigate the phase diagram of color superconducting quark matter with strange quarks (2SC+s quark matter) in beta equliibrium at zero as well as finite temperatures within a Nambu-Jona-Lasinio model. The variational method as used here allows us to investigate simultaneous formation of condensates in quark--antiquark as well as in diquark channels. Color and electric charge neutrality conditions are imposed in the calculation of the thermodynamic potential. Medium dependance of strange quark mass plays a sensitve role in maintaining charge neutrality conditions. At zero temperature the system goes from gapless phase to usual BCS phase through an intermediate normal phase as density is increased. The gapless modes show a smooth behaviour with respect to temperature vanishing above a critical temperature which is larger than the BCS transition temperature. We observe a sharp transition from gapless superconducting phase to the BCS phase as density is increased for the color neutral matter at zero temperature. As temperature is increased this however becomes a smooth transition.

hep-ph↗

arXiv2004

Chiral symmetry breaking, color superconductivity and gapless modes in 2SC+s quark matter

We investigate the chiral symmetry breaking and color superconductivity in color and electric charge neutral quark matter including strange quarks (2SC+s quark matter) in a Nambu-Jona-Lasinio model using a variational method. The methodology involves an explicit construction of a variational ground state and minimisation of the thermodynamic potential. Simultaneous existence of a mass gap and a superconducting gap is seen in a small window of quark chemical potential within the model when charge neutrality conditions are not imposed. Enforcing color and electric charge neutrality conditions gives rise to the existence of gapless modes in 2SC+s quark matter depending upon the magnitude of the gap and the difference of the chemical potentials of the condensing quarks. Within the window for gapless modes, it is seen that the strange quark density can be as large as 30%--40% of the number density of either of the condensing light quarks.

hep-ph↗

arXiv2004

Interior gap superfluidity in a two-component Fermi gas of atoms

A new superfluid phase in Fermi matter, termed as "interior gap" (IG) or "breached pair", has been recently predicted by Liu and Wilczek [Phys.Rev.Lett. {\bf 90}, 047002 (2003)]. This results from pairing between fermions of two species having essentially different Fermi surfaces. Using a nonperturbative variational approach, we analyze the features, such as energy gap, momentum distributions, and elementary excitations associated with the predicted phase. We discuss possible realization of this phase in two-component Fermi gases in an optical trap.

cond-mat.other↗

arXiv2004

Dilepton emission rates from hot hadronic matter

The vacuum polarisation effects from the nucleon sector lead to large medium modifications of the vector meson masses in the Walecka model. With a quantum hadrodynamic framework including the quantum effects, and using a quasiparticle description for quark gluon plasma(QGP), the dilepton emission rate from the hot and dense matter resulting from relativistic nuclear collisions is calculated. Using a model for the fireball evolution which has been shown to reproduce other observables such as charmonium suppression, photon emission and the abundance of hadronic species, we compare with the dilepton invariant mass spectrum measured by the CERES collaboration at CERN SPS. We also compare the results to a previous calculation where the spectral function of a virtual photon (a key ingredient for the emission rate) has been calculated in a chiral SU(3) model.

nucl-th↗

arXiv2003

Chiral symmetry breaking, color superconductivity and color neutral quark matter: a variational approach

We investigate the vacuum realignment for chiral symmetry breaking and color superconductivity at finite density in Nambu-Jona-Lasinio model in a variational method. The treatment allows us to investigate simultaneous formation of condensates in quark antiquark as well as in diquark channels. The methodology involves an explicit construction of a variational ground state and minimisation of the thermodynamic potential. Color and electric charge neutrality conditions are imposed through introduction of appropriate chemical potentials. Color and flavor dependent condensate functions are determined through minimisation of the thermodynamic potential. The equation of state is calculated. Simultaneous existence of a mass gap and superconducting gap is seen in a small window of quark chemical potential within the model when charge neutrality conditions are not imposed. Enforcing color and electric charge neutrality conditions gives rise to existence of gapless superconducting modes depending upon the magnitude of the gap and the difference of the chemical potentials of the condensing quarks.

hep-ph↗

arXiv2002

In-medium vector meson properties and low-mass dilepton production from hot hadronic matter

The in-medium properties of the vector mesons are known to be modified significantly in hot and dense hadronic matter due to vacuum polarisation effects from the baryon sector in the Walecka model. The vector meson mass drops significantly in the medium due to the effects of the Dirac sea. In the variational approach adopted in the present paper, these effects are taken into account through a realignment of the ground state with baryon condensates. Such a realignment of the ground state becomes equivalent to summing of the baryonic tadpole diagrams in the relativistic Hartree approximation (RHA). The approximation scheme adopted here goes beyond RHA to include quantum effects from the scalar meson and is nonperturbative and self--consistent. It includes multiloop effects, thus corresponding to a different approximation as compared to the one loop approximation of including scalar field quantum corrections. In the present work, we study the properties of the vector mesons in the hot and dense matter as modified due to such quantum correction effects from the baryon as well as scalar meson sectors. These medium modifications of the properties of the vector mesons are reflected, through the shifting and broadening of the respective peaks, in the low mass dilepton spectra. There is broadening of the peaks due to corrections from scalar meson quantum effects as compared to the relativistic Hartree approximation. It is seen to be rather prominent for the $ω$ meson in the invariant mass plot.

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arXiv2001

Vector meson masses in hot nuclear matter : the effect of quantum corrections

The medium modification of vector meson masses is studied taking into account the quantum correction effects for the hot and dense hadronic matter. In the framework of Quantum Hadrodynamics, the quantum corrections from the baryon and scalar meson sectors were earlier computed using a nonperturbative variational approach through a realignment of the ground state with baryon-antibaryon and sigma meson condensates. The effect of such corrections was seen to lead to a softer equation of state giving rise to a lower value for the compressibility and, an increase in the in-medium baryonic masses than would be reached when such quantum effects are not taken into account. These quantum corrections arising from the scalar meson sector result in an increase in the masses of the vector mesons in the hot and dense matter, as compared to the situation when only the vacuum polarisation effects from the baryonic sector are taken into account.

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